Filtering the records for a particular client is quite simple. When you login with Security Assist you will have the userID stored in a session variable. On your results page for users to view their own clients you will need to filter the main recordset based on the userID.
If you open the rs and at the bottm you would select to filter it by the userID column where it is equal to a session variable, then just supply the name of your session variable that holds the userID. If you do not know what it is you can check on the user login page, the authenticate user server behavior on this page will list the session variables that are created when the user logs in.
As for the menu, if you setup the three pages with the access rules like I mentioned previously you will want to link only to the director page, with the access restriction rules in place the user will end up at the correct page for them based on their access level. Post back with any additional questions that you have about this.